A convenient and versatile approach to 2,3-dihydro-4H-pyran-4-ones via tandem aldol reaction-conjugate addition

Asymmetric Aldol/Vinylogous Aldol/Cyclization Reaction Using Phosphine Oxide Catalysts

Chiral phosphine oxide sequentially activates silicon tetrachloride and trichlorosilyl enol ethers to facilitate asymmetric aldol/vinylogous aldol reaction of 4-methoxy-3-penten-2-one and conjugated aldehydes in a highly enantioselective fashion, and the subsequent cyclization produced optically active 2,6-disubstituted 2,3-dihydro-4-pyranones bearing stereogenic centers at a remote position in a single operation.

A versatile strategy for the synthesis of 2,6-disubstituted dihydropyranones

A concise synthesis of 2,6-disubstituted dihydropyranones was developed. This sequence is based on the Smith three-component dithiane linchpin coupling strategy. By simply switching the order of epoxide addition in the linchpin coupling step, two analogous dihydropyranones were prepared in good yield from the same starting materials. This sequence allows for considerable flexibility in the nature of R(1) and R(2) groups, which facilitates the preparation of a diverse array of 2,6-disubstituted dihydropyranones.